1. Field of the Disclosure
The disclosure generally relates to retractable instruments having a two stage protraction/retraction sequence and specifically relates to cap-less writing instruments having two stage protraction/retraction sequence.
2. Related Technology
Markers and other writing instruments having volatile inks generally prevent evaporation of said inks by sealing a nib, or other writing point, of the writing instrument from the environment. Traditionally, such markers and writing instruments utilized a removable cap for covering and sealing the writing point. Such arrangements are cumbersome to use, however, as two hands are needed to remove or attach the cap. Additionally, the cap was prone to loss when removed from the writing instrument.
To solve the cap problem, “cap-less” writing instruments have been developed. One example of a cap-less writing instruments is disclosed in U.S. Pat. No. 5,048,990, which is hereby incorporated by reference. The cap-less writing instrument includes a writing member having a writing point. The writing member is accommodated in a seal cylinder that is disposed inside a writing instrument body. A seal cover for closing an end opening of the seal cylinder is disposed on the seal cylinder near the front end of the seal cylinder. A writing member moving mechanism moves the writing member forwardly and locks the writing member at a writing position with the writing point protruding through the front of the writing instrument body. The moving mechanism includes a thread-like member (e.g., monofilament line) that connects the writing member to the seal cover so that after the writing member is retracted, the seal cover is pulled backwardly so as to be brought into contact with the seal cylinder, thus preventing the writing point from drying out when the writing point is in the retracted position. Prior art cap-less writing instruments, such as the writing instrument disclosed in U.S. Pat. No. 5,048,990, are difficult and expensive to assemble and such cap-less writing instruments rely on the writing point to open the seal cover during extension of the writing point. Eventually ink builds up on an inner surface of the seal cover and this buildup of ink can cause a breach in the seal between the seal cylinder and the seal cover, thus leading to premature drying of the writing point. Moreover, the monofilament line was subject to fatigue failure from repeated uses, and must be positioned over the seal cover by hand.
In order to overcome some of the aforementioned problems with previous cap-less writing instruments, cap-less writing instruments were developed that replaced the monofilament closure device with a cover holder having an upper ring and a lower ring connected by a plurality of supports, as shown in U.S. Pat. No. 6,981,812, which is hereby incorporated by reference. The supports were of a rigid construction and the cover holder was disposed on a supporting device. A valve and spring were disposed within the cover holder forming a sub-assembly consisting of the valve, spring, cover holder and the supporting device. The sub-assembly was disposed on a reservoir holder. While this construction solved some of the problems in prior art cap-less writing instruments, the device shown in U.S. Pat. No. 6,981,812 remained relatively complicated and expensive to manufacture because of its many parts and sub-assemblies. Further, because the supporting device is movably disposed on the reservoir holder, manufacturing reproducibility was difficult to optimize because the cover holder/valve/spring/supporting device sub-assembly can become dislodged/damaged during the assembly process. Adequate slack in the internal assembly can also potentially allow the reservoir holder to move back through the valve far enough to breach the seal during the lifetime of the device. Thus, the writing instrument is subject to failure due to possible separation of the supporting device from the reservoir holder.